The present invention relates to seed planting assemblies in general, and in particular relates to a method and apparatus for maintaining seed trench consistency during seed planting operations.
A plurality of seed planting units (also known as row units) are typically supported on a laterally extending tool bar. The tool bar is typically coupled to a tractor or like vehicle suitable for towing the planting assembly along a field that is to be seeded to a crop. Each planting unit includes a device, such as one or more disks, for opening a seed trench in the ground as the tractor draws the tool bar across a field to be seeded. Each planting unit further includes a seed meter to dispense seeds at a controlled rate into a seed trench as the meter is advanced above and along the seed trench during operation. Generally, seeds are delivered to the metering assembly from a seed hopper located on the planting unit or, alternatively, from a smaller container fed from a centralized large hopper used to feed all or a portion of the planting units. Each planting unit further includes a closing assembly that moves soil at the sides of the seed trench to close the seed trench over the planted seeds. Adjacent planting units are laterally spaced a sufficient distance to form seed trenches that are spaced a corresponding distance apart that is suitable for the type of seed being planted.
It should be appreciated that a crop yield is maximized when all seeds emerge from the soil within a given timeframe relative to each other. Otherwise, if some seeds emerge later than others in a given row, the yield for that row can be substantially reduced. One known method for encouraging uniform seed emergence is to maintain the seed trench at a constant depth when performing seed planting operations. Seed trench depth is typically controlled by one or more gauge wheels that ride along the ground and have a predetermined vertical position relative to the seed trench opening device.
Unfortunately, numerous occurrences can cause the seed trench depth to decrease during a conventional planting operation. For instance, if one of the gauge wheels (or a single gauge wheel) encounters an object that projects above the soil surface (e.g., a rock, hard patch of soil, heavy residue covering the soil, etc . . . ), the planting unit is lifted out of the ground by the gauge wheel, thereby forcing the opener disk(s) out of the ground and producing an inconsistent seed trench depth. The corresponding vibration after the initial shock can also affect seed trench depth. Furthermore, the projecting object causes substantial acceleration forces to the planting unit that can cause metering accuracy degradation, and furthermore can create shock loads that degrade the row unit components.
Another difficulty is experienced when operating conventional planting units in hard compacted soils. Specifically, the opener disks typically create an upwards force that biases the planting unit out of the ground. This upwards force is greater in hard soil, and can overcome the weight of the planting unit. In these cases, therefore, the weight of the planting unit is insufficient for the purposes of keeping the gauge wheel(s) in contact with the soil surface, and the planting unit therefore may ride out of the ground, thereby decreasing the seed trench depth. This problem is conventionally addressed by providing springs or additional weight to add force to the planting unit which has the detrimental effect of causing a greater load to be supported by the opener disk(s). As a result, when the opener disk(s) encounters obstacles in the soil, a vibration or shock force is transmitted to the planting unit which, in turn, adversely affects the accuracy of seed trench depth metering, and further can cause damage to the disk opener assembly.
What is therefore needed is a more reliable method and apparatus for maintaining a consistent seed trench depth during operation while minimizing the adverse effects on the planting unit components.